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Watch Balance 

and its 

Jeweling 

(ILLUSTRJITE'D) 




4 







Lecture by C. T. Higginbotham, Supt. 
5uth Bend Watch Company, before the 
tote Convention of Iowa Retail Jewelex*s, 
t Des Moines, Iowa, June 26th, 1907 



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CHARLES T. HIGGINBOTHAM 



Mr. Higginbotham probably has a more thor- 
ough and broader experience in the science of 
making high-grade watches than any other man 
in the United States. 

Although sixty-five years of age, he takes an 
active part in all matters that concern the pro- 
duction of a movement that is gaining a reputa- 
tion as a mo£t accurate and durable timepiece— 
the South Bend. 



THE 

WATCH BALANCE 

AND ITS 

JEWELING 




A Lecture by Q T. Hig^inbotham, 5upt. 
5outh Bend Watch Company, before 
the State Convention of Iowa Retail Jew- 
elers, at DesMoines, la., June 26, 1907. 



TS5-- 






This little booklet contains the 
first of a series of lectures delivered 
by Mr. Higginbotham before various 
Conventions of the Retail Jewelers' 
Associations, and is passed to you, 
feeling it might be of interest. 

Gift 

hop 

(on) 
MAR 27 T9tr 



\T 




HE balance is the heart of the 
watch. As the heart controls 
and regulates the flow of blood 
through the human system, so 
the balance controls and regu- 
lates the flow ©f power through the train 
and escapement of the watch. As the phy- 
sician in diagnosing the ailment of his pa- 
tient directs his attention to the pulse beats, 
so the watchmaker in examining a watch 
submitted to him for inspection directs his 
attention to the vibration of the balance; 
and as a feeble pulse is a certain indication 
of an enervated condition of the human 
mechanism, just so surely a sluggish motion 
of the balance indicates a disordered con- 
dition of the watch. And what an enor- 
mous amount of work a balance performs. 
How few of us thoroughly appreciate it. 
When we say a balance gives 157,680,000 
vibrations every year the statement gives 
but an imjMfrfect idea of the fact. The num- 
ber exmJIsed is too great to be readily 
graspe^^ Let us see if a few comparisons 
will aid us to a better comprehension of it. 
The human heart beats about 65 times 
a minute; a balance 300 times. Thus it 
will be seen that a balance beats more 
than 4% times as fast as the human heart. 
The periphery of an 18 size balance, in de- 
scribing its vibrations, traverses a distance 
of more than 9% miles in 24 hours. This is 
to say that if the balance were rolled along 
the ground to the extent of its vibrations 
it would cover that distance every 24 hours. 



If a track were laid around the world at 
the equator and an eng:ne having six foot 
driving wheels were placed on this track 
and run till the wheels had made the same 
number of revolutions that the balance de- 
scribes, in one year it would have made 
28 complete circuits of the globe. 

The motion of a watch train is inter- 
mittent. The motion of a balance is prac- 
tically continuous. Five times every second 
the train starts up from a dead rest and 
for an extremely brief space of time moves 
forward; again coming to a dead rest. Five 
times every second the balance reverses 
the direction of its rotation, stopping for so 
brief a period that it is impossible lor the. 
eye to detect the instant of its stoppage. 
The office of the train is to convey the 
power stored up in the mainspring barrel to 
the escapement and by this means deliver 
these intermittant impulses to the balance. 
The balance, by its vibrations, determines 
the duration of the intervals of time be- 
tween these successive impulses. As ' ac- 
curacy of rate is entirely dependent upon 
the uniformity of these intervals it follows 
that all conditions which in any manner af- 
fect the motion of the balance must be as 
favorable as possible. The weight of the 
balance should be correctly proportioned to 
the force which impels it. By "weight of 
the balance" I am not to be understood as 
meaning its avoirdupois, but what I shall 
terms its effective weight. By effective 
weight I mean the force of its momentum 
in overcoming the resistence of the hair- 
spring. It is obvious that two balances 



may be identical in weight, yet being of un- 
equal dimensions, the larger one will — be- 
cause of the greater distance of its weight 
from the center — require a hairspring of 
greater strength to bring it to time. It is 
also true that two balances may be identical 
both in weight and diameter, yet one 

having the mean of its weight further from 
the center than the other will also require 
a stronger hairspring. This will be readily 
understood if we consider the effect upon 
the time of a watch produced by moving 
the meantime screws. 

When we move a meantime screw we 
do not alter the weight of the balance nor 
do we alter its dimensions, but we do 
change the distance of the mean of its 
weight from the center and this is what 
produces the change of rate. There is in 
every balance a point — or rather circle — 
somewhere between its center and its 
periphery where, if all its weight were con- 
centrated, its resistence to the tension of 
the hairspring would remain unchanged and 
as a consequence its vibration would be 
performed in the same time. This point is 
called the radius of gyration. The law 
which determines the effect of the radius 
of gyration is common to all bodies vibrat- 
ing from or rotating around a fixed point 
This law enters into the motion of the 
planetary system : in fact the entire universe. 
The laws which govern the oscillation of 
the pendulum are, in this respect, similar 
but in another respect they differ mater- 
ially. This difference is in the fact that the 
resistance offered to the oscillation of the 



pendulum is gravity and friction, mainly 
gravity, as the friction is simply the re- 
sistance of the atmosphere. Gravity, how- 
ever, has no effect on the vibration of a 
poised balance, the resistance it has to over- 
come is the tension of the hairspring, the 
friction of its pivots in their bearings and 
the resistance of the atmosphere; mainly 
the tension of the hairspring. The conse- 
quence is that a difference in weight has no 
effect on the oscillation of a pendulum, pro- 
vided the mean of the weight is located 
at the same distance from the point of 
suspension. Two pendulums of different 
weights will vibrate in exactly the same 
intervals of time provided the point known 
as the center of oscillation be the samt. 
distance from the point of suspension. The 
center of oscillation is not the center of 
gravity, but differs slightly from that point, 
being a point where if its entire weight 
were concentrated it would occupy the same 
time for its vibration. In a balance, how- 
ever, the time of its vibration is affected, 
not only by the length of the radius of 
gyration, but also by its weight. If a bal- 
ance be too light the extent of the arcs of 
vibration will be too sensitive to variations 
of power, which as we all know occur be- 
tween the winding up and running down of 
the mainspring; this sensitiveness will very 
much increase the isochronal error. If too 
heavy the arcs of vibration will be too short, 
and the watch will have what is commonly 
called a poor motion. It is also necessary 
that the rim should be sufficiently rigid to 
offer all resistance possible to flexure. A 

6 



balance having a arc of vibration of a turn 
and a quarter develops considerable centri- 
fugal force. The effect of this is to deflect 
the rim outward and as the motion reverses 
it springs inward again. This serves to 
quicken the long arcs of vibration, thus in- 
creasing the difficulty of isochronising. 

There is so much dependent upon the 
proper construction of a bi-metalic, or com- 
pensation balance, sometimes called chrono- 
meter balance, that a brief description of its 
manufacture will aid us to the better un- 
derstanding of its functions. The construc- 
tion of a compensation balance is a triumph 
of science and mechanical ingenuity. Its 
functions are twofold — First, by its mo- 
mentum, in connection with the resistance 
of the hairspring, to control the motion of 
the train wheels. Second, by automatically 
changing the radius of its gyration to com- 
pensate for its own expansion and contrac- 
tion and changing elasticity of the hairspring 
caused by variations in temperature. This 
is to say the mean of its weight is auto- 
matically insured at the correct distance 
from the center to overcome this varying 
tension. It is of the first importance that 
the two metals, steel and brass, of which 
a balance is composed should be selected 
with the utmost care. A freedom from 
flaws and an absolute uniformity of texture 
is necessary. Special formulas are used 
for the mixture of these metals and every 
process in the manufacture of the balance 
calls for great precision. The slightest neg- 
lect is likely to be disastrous to its effic- 
iency as a means of adjustment. 



The brass used in a compensating bal- 
ance should have twice the co-efficient of 
expansion as the steel. A strip of this steel 
is placed under a punch and cut into disc&. 
These discs are called balance blanks. A 
hole is now drilled in the center of the 
blank and is carefully opened to exact size. 
Upon the accuracy of this operation de- 
pends to a large extent the truth of the bal- 
ance. After being once opened it is not 
touched with a cutting tool of any descrip- 
tion until the balance is completed. The 
blank is now placed upon an absolutely true 
arbor and the outside turned down to the 
standard size; a ten thousandth of an inch 
being taken into account in this measure- 
ment. A ring of brass is now formed; the 
inside of said ring being carefully fitted to 
the outside of the steel blank. 

Both blank and ring are now dipped 
into a specially prepared flux and are driven 
together. These are placed in a sort of 
bottomless cup called a capsule. The metal 
of which this capsule is composed has a 
much higher point of fusion than the brass, 
the object being to retain the brass in posi- 
tion when it is melted. The hole in the 
steel blank is now filled with a preparation 
of plumbago to prevent oxidization in the 
subsequent operation of heating. The em- 
bryonic balance is now placed in a muffle 
and heated until the brass fuses and be- 
comes smelted to the steel blank. After 
cooling the plumbago is removed from the 
hole and the balance mounted on an arbor 
and a turning made on its edge which re 
moves the capsule and a portion of the 



brass. In this condition the brass is quite 
soft and it remains to bring it to the proper 
density; an operation requiring the utmost 
care and skill. If not sufficiently compress- 
ed the finished balance will be soft and 
will easily get out of true ; if too much com- 
pressed the brass will be more or less dis- 
integrated; its cohesion impaired and its ac- 
tion under changes of temperature very un- 
certain, thus rendering it unfit for adjust- 
ment. 

The compression of the brass is per- 
formed in a machine of special design and 
construction. This machine is provided 
with rolls which gradually compress the 
brass at the same time producing a lam- 
ination in its grain which adds greatly to 
its rigidity. The sides of the balance are 
now faced off and the steel chambered to 
nearly the finished depth. It is now plac- 
ed in a die under a punch and the metal 
between the arm and rim punched out. 

The next operation is the drilling and 
tapping of the holes in the rim for the re- 
ception of the screws. The balance is now 
finished, polished, the screws placed in posi- 
tion and is ready to be mounted on its 
staff. 

Another method for uniting the blank 
and ring is to introduce between the two 
a thin strip of pure silver. It is impossible 
to secure a perfect fit in this manner. The 
result is that balances where the metals 
are united by interposing silver or solder 
are not usually perfectly united. There 
are spaces here and there where a perfect 
union has not taken place. These are called 



blow holes. Sometimes they show on a 
finished balance giving it an unsightly ap- 
pearance but when even this is not the case 
they cause irregularity in the action of the 
rim under temperature changes. It is hard- 
ly necessary to say that if both sections of 
the rim do not expand and contract equally 
the balance will retain its poise only in the 
particular temperature in which the opera- 
tion of poising was performed. 

Another method which is pursued by 
manufacturers for hardening the brass is 
hammering. The effect of this method is 
to compress the outer molecules leaving 
those near the blank much less dense. It is 
practically impossible to make a rigid bal- 
ance in this manner, and for two reasons. 
First, if the hammering is continued for a 
sufficient length of time to harden the brass 
entirely through, the compression is carried 
to the steel blank decreasing its diameter. 

This, of course, produces an imperfect 
balance. The proper proportions of steel 
and brass in the finished balance are ap- 
proximately two-fifths steel and three-fifths 
brass. If the steel is compressed as is the 
case frequently when the balance is ham- 
mered the finished balance will have a smal- 
ler percentage of steel. Second, if the 
brass is hammered to the ordinary extent 
it will not be hardened entirely through, 
and the finished turning removing a large 
percentage of the compressed metal, what 
remains is almost as soft as before being 
treated. 

We shall now take up for consideration 
the balance staff. 

10 



The steel of which the staff is made 
should be of a very fine texture. The 
amount of carbon infused into it should be 
sufficient to produce a perfectly hard metal 
under the usual treatment, but an excess of 
carbon is to be carefully avoided. I shall 
have occasion a little later on to speak of 
the danger of too much carbon. The tem- 
per should be such that a pivot will break 
rather than bend. It is rarely that a pivot 
which has been bent can be straightened 
to restore it to its normal condition. In 
our factory we never make the attempt and 
I should recommend this course in all cases 
where accuracy of time is the prime object. 
The balance pivots should be of sufficient 
length to carry the cone well clear of the 
jewel; otherwise the oil is apt to run down 
the staff. They should be of a uniform 
diameter for a distance of at least one hun- 
dredth of an inch from the ends. That is 
they should be neither front or back taper. 
This will avoid trouble in variation of side 
shake and is particularly necessary if the 
endshake happens to be a little long. An- 
other matter upon which too much stress 
cannot be laid is that the pivots be absolute- 
ly in line with each other. A reference to 
the sketch will clearly show what is meant. 

You will notice a black line running 
through the center of the staff and also 
through the center of one pivot but consider- 
ably out of center with the other pivot. 
This is technically called out of line and is 
invariably the result of a faulty method of 
manufacture. It can frequently be detect- 
ed by a rattling sound when the watch is 



held to the ear. This should not be con- 
founded with a grinding sound which is due 
to an entirely different cause; generally a j 
poorly polished pivot, or a rough jewel hole. 
A balance pivot in this condition will pre- 
clude the possibility of perfectly poising 
the balance and will interfere with the ad- 
justment of the watch. 

The best method of making a balance 
staff is as follows: The spindle is mounted 
in a tube called a quill. This tube is of 
sufficient thickness to make it perfectly 
rigid; cone bearings are provided at both 
ends. One end of this spindle carries a 
jeweled center having a V shaped recess 
surrounded by a ring or shell of metal as 
shown in the drawing. One of the pointed 
ends of the staff is pressed into this jewel 
while the piece is being shellaced into 
position, during which process the outer 
end is perfectly trued; one pivot is now 
ground up and polished, no turning tool 
being used for this purpose. The staff is 
now reversed, the pivot just formed being 
pressed into the jewel center and the other 
pivot ground up and polished in a similar 
manner. This secures an absolute align- 
ment of the pivots both with the staff and 
with each other. 

I have spoken of the danger of an ex- 
cess of carbon in the steel of which the 
staff is made. You have all doubtless been 
troubled to some extent by balance pivots 
cutting into the end stones, termed pitted 
endstones. The pitting of endstones may 
be the result of many defects. For in- 
stance, diamond powder will pit an end- 



stone. A roughly finished or porous end- 
stone will often produce the same result. 
The cause being that small particles of the 
stone become detached and mingling with 
the oil form an abrasive compound. 

Oilstone powder or flour of emery will 
pit an endstone provided it is of soft ma- 
terial such as garnet, but it will not pit a 
sapphire endstone. No other material 
should be used in watches. I will now 
speak of the most fruitful of all causes for 
pitted endstones, and one which is not gen- 
erally understood. This is the composition 
and treatment of the steel itself. 

Some years ago exhaustive experiments 
were conducted to ascertain if possible the 
source of this most serious and generally 
unaccountable trouble. In the course of 
these experiments it was found that certain 
balance staffs would pit endstones despite 
the greatest care exercised in the selection 
of the stone and its finish. Indeed, it 
sometimes prevailed to such an extent as to 
pit a diamond. This phenomenon could not 
be accounted for by any of the then known 
theories and it was necessary to look to 
other causes than those mentioned for the 
trouble. Turning attention to the steel and 
its treatment the discovery was made that 
steel possessing a large percentage of car- 
bon, when brought to a very high heat in 
being hardened invariably, in time, pitted 
the hardest endstones. The experiments 
were continued, many of them being repeat- 
ed over and over again for long periods with 
the same result. 

13 



It is a well known fact that diamond is 
nothing more than crystalized carbon, and 
this taken in connection with the results 
obtained by the experiments just mentioned 
seems to fully justify the theory that the 
pitting of endstones may be, and often is 
produced, by a portion of carbon contained 
in the steel being transformed by excessive 
heat into minute diamonds; or at least into 
crystals having almost as high an abrasive 
quality. We have since used the utmost 
care in selecting the steel and in avoiding 
overheating in the process of hardening, 
with the result that a pitted endstone is 
now an extremely rare occurrence with us. 

The jewels used in watches are usually 
garnet, ruby and sapphire. Their hardness 
being in the order named. • Sapphire is next 
to diamond in hardness and is the only 
stone that should be used for balance jewels 
and endstones. MK^ tx^t; Ax_A-~i^— <jL*. "V 

We will presume that the diameters of 
the pivots are properly proportioned to the 
dimensions and weight of the balance, 
which for an 18 size may be eleven to 
twelve hundredths of a millimeter. The 
proper endshake for a staff is about two 
hundredths of a millimeter. H+*r l " ~**'«> 

The shape of the jewel hole is of the 
first importance. The best results cannot 
be obtained where a hole having parallel 
Bides is used for the reason that a very 
slight thickening of the oil will impede the 
motion of the balance unduly. 

They should be what is known as olive 
holes as represented in sketch. This shape 
reduces the retarding effect of thickening 



oil to the minimum. The face of the jewel 
should have a hemispherical oil cup and the 
back should be well rounded. When in 
position the distance between the jewel and 
endstone should be about two hundredths of 
a millimeter. If this distance is too great 
the jewel will soon become dry for a rea- 
son which I will explain a little later on. 
H is a very bad practice to allow the jewel 
and endstone to be in actual contact as you 
will sometimes find in the cheapest foreign 
work. This prevents the oil flowing freely 
about the end of the balance pivot where 
it is most needed. The advantage of hav- 
ing the back of the balance jewel well round- 
ed and at a slight distance from the end- 
stone is that the balance pivot will by this 
means be supplied with oil from capillary 
attraction. The law of capillary attraction 
causes liquids to seek the narrowest space. 
If we insert a very small glass tube into a 
tumbler of water, holding the tube per- 
pendicularly, we shall find that the liquid 
will rise to a slightly higher point inside 
the tube than the surrounding surface. 

Capillary attraction is the force that 
causes this phenomenon. If we bring two 
edges of a couple of plates of glass together 
allowing the surfaces to slightly diverge 
from each other and holding them in this 
position with their contracting edges upper- 
most insert them in water, we shall find 
that on withdrawing them a certain amount 
of water will, in spite of the force of grav- 
ity, be retained by the close proximity of 
the inner surfaces of the glass. The law 
is the same as that which causes the liquid 

15 



to rise in a glass tube. It is the effect of 
this law which retains oil between the end- 
stone and jewel. Were it not for this na- 
tural force the oil would soon flow away 
from the jewel hole leaving the balance 
pivot dry. If the upper side of a balance 
jewel be flat the greater portion of the oil 
will be drawn between the settings leaving 
the jewel dry, whereas if the jewel be well 
rounded the oil will collect at the center 
and the balance pivots acting as the piston 
of a pump keep the supply at this point 
until the last particle is exhausted. The 
illustration shows a little device which fully 
illustrates this law. 

Avoid putting too much oil to a balance 
jewel. A super-abundance of oil will either 
run down the balance staff or find its way 
between the jewel settings. Excellent re- 
sults may be secured by moistening with 
oil the point of a piece of pegwood sharp- 
ened to enter the balance jewel hole and 
with the usual oiling with a steel oil drop- 
per insert the peg into the balance hole. 
A portion of the lubricant is thus carried 
to the space between the balance jewel 
and endstone. 



When you have read this little 
booklet from cover to cover, by pass- 
ing it to your watch-maker, it might 
be to your mutual advantage. 



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